1. Field of Invention
The invention relates to an ink chamber doctor blade for acting upon an ink transfer roll of a rotary press with a fluid.
2. Description of the Prior Art
Such ink chamber doctor blades are used in different types of rotary printing presses, for example in flexographic and rotogravure printing presses. These types of ink chamber doctor blades consist in general of an ink chamber extending in the axial direction of the ink transfer roll, whereby, during the printing operation, the ink chamber is filled with ink. The ink chamber doctor blade can also be filled with a different fluid, for example with a cleaning liquid, if the ink transfer rolls are to be cleaned. On the longitudinal side of this ink chamber, in general two doctor blades are attached, which are in contact with the ink transfer roll during the operation. Both doctor blades form the boundary of a gap extending in the axial direction of the ink transfer roll, through which the ink can pass on to the surface of the ink transfer roll. Further, ink chamber doctor blades are as a rule closed on the front side with sealing elements, which prevent leakage of ink from the sides. Thus the system, consisting of the ink chamber, doctor blade, ink transfer roll and the seals on the sides, forms a closed system, to which the ink is in general supplied through the feeding lines and removed through the discharge lines. During the printing operation, the ink chamber doctor blade is normally filled completely, or at least to a major part.
In the case of the flexographic printing machines, the ink transfer roll, which interacts with the ink chamber doctor blade in the manner described above, is the so-called anilox roll, which is provided with several small saucers along its outer circumference. These saucers, if they are in the area of the ink chamber doctor blade, get filled with the ink and carry the latter with it. In order to ensure that only the saucers are filled with ink and that the other areas of the exterior surface of the anilox roll also do not take up ink, this surplus ink is removed by one of the two doctor blades. This doctor blade is therefore called working doctor blade. The second doctor blade has solely the function of closing the doctor blade chamber on the outside and is called locking doctor blade. In flexographic printing method, the anilox roll transfers the ink onto the printing block affixed on the format roll, which printing blocks, on their part, deliver the ink onto the substrate to be printed. One such system has already been described in greater detail by the present applicant in the patent application DE 101 50 488 A1.
But in other printing methods also, ink chamber doctor blade/ink transfer roll-systems have been employed. For example, in rotogravure printing presses, the printing cylinder is the ink transfer roll, which takes up the ink, whereby the ink transfer roll already carries the printing blocks, which are worked in as grooves in the outer surface of the printing cylinder. The printing ink taken up by these grooves is directly applied on the substrate to be printed.
The grooves of a printing cylinder, or the saucers of an anilox roll, which have delivered their ink, bring in air into the ink chamber doctor blade, which air swirls in there and hampers refilling of the grooves or the saucers with fresh ink. This effect intensifies with increasing printing rate. For this reason, DE 38 23 340 C1 suggests that one more doctor blade be provided in the interior of the doctor blade chamber. DE 198 00 840 A1 also shows one such arrangement. On one hand, the ink chamber is subdivided into several compartments in the chamber by this or these additional doctor blade(s), so that the air-ink mixture remains in one compartment of the chamber, while in the other compartments, the saucers are completely filled with fresh ink. On the other hand, such additional doctor blades can press the ink into the saucers or the grooves.
However, in the mentioned publications, no details about the embodiments are available about how the additional doctor blades are fastened in the ink chamber doctor blade. In practice however, use of a third blade or more doctor blades is known, which are either screwed on directly or which can be held in clamped fashion by means of holding strips, whereby the holding strips are bolted with the doctor blade chamber. Dismounting and fastening of the screws for the purpose of replacement of additional doctor blades is, however, time consuming.